Production of muconodinitrile

ABSTRACT

A high yield (92-95 percent) catalytic process for the production of muconodinitrile (1,4-dicyano-1,3-butadiene) by oxidative vapor phase dehydrogenation of 1,4-dicyanobutenes has been developed. The process is applicable to each of the following starting materials: (a) 1,4-dicyano-1-butene, (b) 1,4dicyano-2-butene, and (c) a mixture of the last two isomers. The preferred catalysts used are supported bismuth phosphomolybdate or bismuth molybdate systems and the range of operating temperature is between 350-580* C. An important feature of the process is that it involves passing the starting material over the catalyst in admixture with a desorbent, in particular, benzene, which does not participate in the reaction but prevents side reactions of the muconodinitrile formed. The isomeric composition of the muconodinitrile depends on the particular starting material and on the reaction conditions.

United States Patent [191 Schmidt, deceased et al.

[ PRODUCTION OF MUCONODINITRILE [75] Inventors: Gerhard J. M. Schmidt,deceased,

late of Rehonst, Israel by Esther Schmidt, legal representative; JosephShabtai, Rehovot; Amiram Hirshfeld, Petah-Tiqua, both of Israel [73]Assignee: Yeda Research and Development Co., Ltd., Rehovot, Israel [22]Filed: Sept. 9, 1971 [211 Appl. No.: 179,209

[30] Foreign Application Priority Data Sept, 17. I970 Israel 35306 [52]U.S. Cl. 260/465.8 R [5l] Int. Cl. C07c 121/02 [58] Field of Search260/4658 R, 465.9, 465.3

[56] References Cited UNITED STATES PATENTS 3,248,340 4/1966 Callahan et260/4653 X 3,445,521 5/l969 Callahan et al 260/4653 X 3,466.3 l 8 9/1969Lambert et al. 260/4659 3,542,842 l l/l970 Grasselli et al. 260/4653June 25, 1974 3,579,559 5/I97l Unger 260/4658 R Prir naryExaminer-Joseph P. Brust Soffen [5 7] ABSTRACT A high yield (92-95percent) catalytic process for the production of muconodinitrile(l,4-dicyano-l,3- butadiene) by oxidative vapor phase dehydrogenation of1,4-dicyanobutenes has been developed. The process is applicable to eachof the following starting materials: (a) 1,4-dicyano-l-butene, (b)1,4-dicyano-2- butene, and (c) a mixture of the last two isomers. Thepreferred catalysts-used are supported bismuth phosphomolybdate orbismuth molybdate systems and the range of operating temperature isbetween 350-580 C. An important feature of the process is that itinvolves passing the starting material over the catalyst in admixturewith a desorbent, in particular, benzene, which does not participate inthe reaction but prevents side reactions of the muconodinitrile formed.The isomeric composition of the muconodinitrile depends on theparticular starting material and on the reaction conditions.

8 Claims, No Drawings PRODUCTION or MUCONODINITRILE BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates to thevapor phase catalytic dehydrogenation of l,4-dicyanobutene to producemuconodinitrile 1,4-dicyano-1,3-butadiene).

2. Description of the Prior Art Muconodinitrilel,4-dicyano-1,3-butadiene) can be prepared on a small scale by severalprocedures. A mixture of the three geometric isomers of muconodinitrileis obtained by treating 2,3-dichloro-1,4-dicyanobutane, or thecorresponding dibromo compound, with sodium acetate according to H. F.Piepenbrink, Ann., 572, 83 (1961 According to .l. H. Hall et al.,J.A.C.S 89, 5836 1967) the thermal decomposition of 1,2- diazidobenzeneyields selectively cis,cismuconodinitrile. According to G. M.J.'Schmidt, Israel Pat. App. No. 31872 gaseous bromine is added to solidl,4-dicyano-2-butene to yield 2,3-dibromo-l,4- dicyanobutane, whichlatter is converted by dehydrobromination in the solid state withgaseous ammonia to muconodinitrile.

The dehydrogenation of mononitriles is known, as for example theconversion of propionitrile to acrylonitrile (Jap. Pat. No. 69 15,765),or the conversion of 1- cyano-Z-butene to l-cyano-l,3-butadiene in thepresence of a phosphomolybdate catalyst (U.l(. Pat. No. 1040308). Asl,4-dicyano-l-butene and also l,4- dicyano-2-butene are availablecommercially, a catalytic process of these to muconodinitrile isespecially attractive. According to the invention there is provided forthe first time a direct catalytic dehydrogenation process for theproduction of the desired product.

DESCRIPTION OF THE INVENTION This invention relates to the manufactureof muconodinitrile l ,4-dicyano-1,3-butadiene), which usually consistsof a mixture of the three possible geometric isomers, i.e.cis,cis-muconodinitrile, cis-transmuconodinitrile, andtrans,trans-muconodinitrile. The invention provides a simple andconvenient process for production of muconodinitrile by vapor phaseoxidative dehydrogenation of l,4-dicyanobutenes at elevated temperatureand in the presence of a suitable catalyst.

The oxidative dehydrogenation process described in this invention isapplicable to each of the following readily available startingmaterials: (a) l,4-dicyano-lbutene, (b) l,4-dicyano-2-butene, and (c) amixture of the last two isomers. l,4-Dicyano-l-butene and 1,4-dicyano-Z-butene, used as starting materials either separately or in theform of a mixture, may each be composed either of the pure cisor of thepure transisomer or of a mixture of cisand trans-isomers. Themuconodinitrile produced from l,4 dicyano-l-butene. orl,4-dicyano-2-butene, or a mixture of these two isomers, is essentiallyfree of by-products under the operational conditions of this process.

The conversion of l,4-dicyanobutene to muconodinitrile is accomplishedin the presence of a catalyst system which may belong to a group ofcatalysts known from the art to be suitable for effecting vapor-phaseoxidative dehydrogenations. Particularly useful for the purposes of thisinvention are bismuth phosphomolybdate and bismuth molybdate catalystsin which the bismuth/molybdenum ratio is 0.8 to 1.0. The catalyst isusually supported on a carrier material, preferably silica. Thepreparation of the supported catalyst system may be performed by avariety of procedures which are known from the art. For example, thecatalyst may be prepared by co-gelling of the various components,preferably in the presence of silicic acid, or an aqueous colloidalsilica! sol, and then dried, calcined at 530600C and subsequently groundto an appropriate particle size. The catalyst may be employed inadmixture with an inert diluent, e.g. quartz chips or Pyrex glasshelices. Preferably, the catalyst may be used in a pelletized form, orin the form of spheres, or in other convenient small particle forms asknown in the art.

The process of the invention may be carried out in any apparatus of thetype suitable for vapor-phase oxidative dehydrogenation. For instance,the dehydrogenation may be performed in a flow system equipped withreactor and designed for either continuous or intermittent operation.The catalyst bed employed in the process may be either a fixed bed or afluidized bed. Although the catalyst may be continuously regenerated byoperation under air, it may be desirable to employ independent periodicreactivation of the catalyst bed by contact with air at 500 to 600C. The1,4- dicyanobutene, preferably dissolved in a solvent such as benzene,may be introduced into the reactor in admixture with a carrier gas,preferably air. The 1,4- dicyanobutene solution is vaporized andcontacted with the catalyst which is maintained at an elevatedtemperature. The benzene may play an important role in desorbing themuconodinitrile produced and inpreventing side reactions.

Temperatures within the range of 350 to 600C may be employed in theprocess, but temperatures between 450 to 580C are preferred.

The process is usually conducted at about atmospheric pressure, butslightly lower or higher pressures may be used. The apparent contacttime employed in the process, i.e. the length of time a unit volume ofvaporized l,4-dicyanobutene is in contact with an apparent unit volumeof catalyst at a given temperature, may vary in the range of 0.1 to 60seconds. The optimal contacttime depends on the operating temperature.For example, in the vicinity of 550 a contact time of 2 to 10 sec. isnecessary for high conversion of the starting material.

The isomeric composition of muconodinitrile produced by the process ofour invention depends to some extent on the nature of the startingmaterial, and apparently, also on the operating temperature and thecontact time. For example, at temperatures in the range of 510 to 570and contact times between 2 to 10 sec. the concentrations of the threeisomeric components of muconodinitrile obtained from l,4-dicyanol-butenevary within the following limits: cis,cismuconodinitrile 40-55,cis,transmuconodinitrile 20-35, and trans,transmuconodinitrile 20-30percent. In the same ranges of operating conditions, the distri butionof the isomeric components of muconodinitrile produced froml,4-dicyano-2-butene varies within the following limits: cis,cis-isomer50-70, cis,trans-isomer 15-25, and trans,trans-isomer l5-28%.

The three geometric isomers of muconodinitrile are separable byfractional crystallization, chromatography, and other methods known fromthe art. Therefore, the method of our invention provides a convenientmethod for preparation of each of the three geometric isomers ofmuconodinitrile, i.e. cis,cis-muconodinitrile,cis,trans-muconodinitrile, and trans,transmuconodinitrile.

Muconodinitrile is a potentially useful starting material forpolymerization and copolymerization' processes.

The invention is illustrated in the following Examples.

EXAMPLE 1 A batch of powdered bismuth phosphomolybdate on silicacatalyst was pre-activated at 600 under air. The catalyst was thendiluted with Pyrex helices, transferred to a reactor and heated to 550.A 15 percent solution of 1,4-dicyano-l-butene in benzene was introducedin the reactor at a constant rate, in admixture with a constant flow ofair. The molar ratio of oxygen to 1,4- dicyano-l-butene maintainedthroughout the process was about 2:1 and the operating pressure wasapproximately atmospheric. The apparent contact time was 2 sec. The1,4-dicyano-l-butene was converted to the extent of 75 percent and theyield of muconodinitrile based on converted starting material was 95percent.

The muconodinitrile produced was composed of cis,- cis-muconodinitrile l.2 percent, cis,transmuconodinitrile 23.8 percent, andtrans,transmuconodinitrile 25.0 percent, as determined by gaschromatography on a 2m X 3mm (i.d.) column filled with 5 percentbutandiol succinate on 40-60 mesh Chromosorb W. The nmr spectrum of theproduct [CDCl;;, 6 5.5-6.1 (m,2), 6.7-7.7 (m,2)] was identical with thatof a sample of muconodinitrile prepared by independent means.

EXAMPLE 2 The catalyst, consisting of powdered bismuth phosphomolybdateon silica, was pre-activated at 600 under air and then diluted withPyrex helices and heated in a reactor to 550. A solution of 1,4-dicyano-2-butene in benzene was introduced at a constant rate in the reactorunder a constant flow of air. A 1:1 molar ratio of oxygen to1,4-dicyano-2-butene was maintained throughout the process, and thecontact time employed was 4 sec. The operating pressure was aboutatmospheric. The conversion of 1,4-dicyano-2-butene was 86 percent andthe yield of muconodinitrile based on converted starting material was 94percent. The isomeric composition of the muconodinitrile was as follows:cis,cis-muconodinitrile 65 percent, cis,transmuconodinitrile 20 percent,and trans,transmuconodinitrile percent.

EXAMPLE 3 A sample of powdered bismuth phosphomolybdate on silicacatalyst was pre-activated at 600 under air and then mixed with quartzchips and heated in a reactor to 550. A benzene solution of1,4-dicyano-lbutene was introduced in the reactor under a constant flowof nitrogen. The apparent contact time employed was 6 sec. Theconversion of 1,4-dicyano-l-butene was 84 percent and the yield ofmuconodinitrile based on converted starting material was 95 percent. Theproduct consisted of cis,cis-muconodinitrile 50.5 percent,cis-trans-muconodinitrile percent, trans, transmuconodinitrile 24.5, andby-products 5 percent.

EXAMPLE 4 The catalyst, consisting of pelletized bismuthphosphomolybdate on silica, was pre-activated at 550 under a flow of airand then heated in a reactor to 570. A solution of 1,4-dicyanol-butenewas introduced into the reactor in admixture with air at a relative ratecorresponding to a 1.5:] molar ratio of oxygen to 1,4- dicyano-l-butenethroughout the process. The apparent contact time used was 3 sec. Theoperating pressure was about atmospheric. The conversion of 1,4-dicyanol-butene was 84 percent and the yield of muconodinitrile basedon converted starting material was 93 percent. The isomeric compositionof the muconodinitrile produced was as follows: cis,cis-isomer 47.2percent, cis,trans-isomer 31.5 percent, and trans,trans-isomer.

21.3 percent.

EXAMPLE 5 The pelletized bismuth phosphomolybdate on silica catalystused in Example 4 was regenerated in situ by heating for 4 hrs. at 580under a flow of air. The temperature was then lowered to 530 and abenzene solution of 1,4-dicyano-2-butene was introduced at a constantrate into the reactor, in admixture with air. A 1.5:] molar ratio ofoxygen to 1,4-dicyano-2-butene was maintained throughout the process andthe apparent contact time employed was 4 sec. The conversion of1,4-dicyano-2-butene was 89 percent and the yield of muconodinitrilebased on converted starting material was 94 percent. The isomericcomposition of the product was as follows: cis,cis-muconodinitrile 50.3

EXAMPLE 6 The catalyst used in Example 5 was reactivated for 2 hrs. at550 under air and then heated in a reactor at 510. An equimolar mixtureof 1,4-dicyano-l-butene and 1,4-dicyano-2-butene was dissolved inbenzene and introduced into the reactor at a constant rate in admixturewith air. A l.8:1 molar ratio of oxygen to 1,4- dicyanobutene wasmaintained throughout the process and the apparent contact time used was3 sec. The conversion of the 1,4-dicyanobutenes was percent and theyield of muconodinitrile based on converted starting material was 92percent. The isomeric composition of the muconodinitrile produced was asfollows: cis,cisisomer 48.6 percent, cis,trans-isomer 30.4 percent, andtrans,trans-isomer 21. 1 percent.

We claim:

1. A process for the production of muconodinitrile(1,4-dicyano-l,3-butadiene) which consists essentially of contactinggaseous 1,4-dicyanobutene with a catalyst selected from the groupconsisting of bismuth phosphomolybdate and bismuth molybdate at atemperature in the range of from 350-600 C. and for an apparent contacttime of 01-60 seconds, said catalyst in admixture with benzene as adesorbing agent.

2. The process of claim 1 wherein the temperature is 450580 C.

3. The process of claim 1 wherein the dicyanobutene is in admixture withair.

4. The process of claim 1 wherein the catalyst has a bismuth tomolybdenum ratio of 0.8 to 1.

5. The process of claim 1 wherein the 1,4- dicyanobutene is in admixturewith air and with ben- 5 6 zene as a desorbing agent, wherein thetemperature is dicyanobutene is 1,4dicyano-2-butene. 450-580 C. andwherein the catalyst hasabismuth to The process of claim 1 wherein themolybdenum mm of to dicyanobutene is a mixture of 1,4-dicyano-l-butene6. The process of claim 1 wherein the 1,4- dicyanobutene is 1,4-dicyan0-l-butene.

7. The process of claim 1 wherein the 1,4-

and 1,4-dicyano-2-butene.

2. The process of claim 1 wherein the temperature is 450*-580* C.
 3. Theprocess of claim 1 wherein the 1,4-dicyanobutene is in admixture withair.
 4. The process of claim 1 wherein the catalyst has a bismuth tomolybdenum ratio of 0.8 to
 1. 5. The process of claim 1 wherein the1,4-dicyanobutene is in admixture with air and with benzene as adesorbing agent, wherein the temperature is 450*-580* C. and wherein thecatalyst has a bismuth to molybdenum ratio of 0.8 to 1.0.
 6. The processof claim 1 wherein the 1,4-dicyanobutene is 1,4-dicyano-1-butene.
 7. Theprocess of claim 1 wherein the 1,4-dicyanobutene is1,4-dicyano-2-butene.
 8. The process of claim 1 wherein the1,4-dicyanobutene is a mixture of 1,4-dicyano-1-butene and1,4-dicyano-2-butene.